共查询到20条相似文献,搜索用时 31 毫秒
1.
《Physics letters. [Part B]》1988,206(1):51-56
Several models of non-abelian orbifolds have been constructed. There are models with three or four families of quarks and leptons, and gauge symmetry SU(3) × SU(2) × SU(2) × U(1)2 × SU(3)′ × SO(10)′ × U(1)′ or SU(3) × SU(2) × U(1)3 × SU(4)′ × SO(8)′ × U(1)′. 相似文献
2.
We extend the supersymmetric, confining theory of weak interactions to a left-right symmetric model. This model is based on the gauge group SU(M)SC×SU(2)R×SU(2)L×SU(3)c×U(1) and is more natural as far as supersymmetry breaking is concerned. Supersymmetry protects chiral symmetries from spontaneous breakdown and allows a solution to the strong CP problem. This model can accommodate at most three generations of quarks and leptons. 相似文献
3.
We propose a composite model for quarks and leptons based on an exact SU(3)C × SU(3)H gauge theory and two fundamental fermions: a charged T-rishon and a neutral V-rishon. Quarks, leptons and W-bosons are SU(3)H-singlet composites of rishons. A dynamically broken effective SU(3)C × SU(2)L × SU(2)R × U(1)B?L gauge theory emerges at the composite level. The theory is “natural”, anomaly free, has no fundamental scalar particles, and describes at least three generations of quarks and leptons. 相似文献
4.
We consider parity violating effects in the neutral sector of a left-right symmetric SU(2)L × SU(2)R × U(1) gauge model of weak and electromagnetic interaction. With four quarks and four leptons, the parity violating optical rotation in atoms is estimated to be about an order of magnitude smaller (and of opposite sign) compared to the Salam-Weinberg (SW) model prediction. However, with new quarks and leptons this effect can be arranged to be even smaller. Weak-electromagnetic interference effects are quantitatively different from those found in the SW model. A unified gauge theory which embeds the left-right symmetric gauge model is briefly discussed. 相似文献
5.
We explore in detail the hypothesis that quarks and leptons are the approximately massless quasi Goldstone fermions of a supersymmetric preon theory. In particular, we discuss the possible patterns of states emerging from the spontaneous breakdown of global symmetries in supersymmetric theories and construct the low-energy effective lagrangians describing the interaction of these states. In contrast to what happens in the Goldstone sector, the interactions of the quasi Goldstone fermions contain arbitrary parameters which directly reflect the preon dynamics. Various models are explored, including both models in which the weak interactions are residual and models where these interactions are fundamental. A variety of issues are addressed, from the universality and approximate SU(2)L nature of the weak interactions, for the former class of models, to the generation of states beyond the quarks and leptons and the nature of the dynamical breaking of SU(2)L×U(1), for the latter class of models. Open questions and speculations connected with the origin of families and the nature of fermion mass generation, including supersymmetry breaking, are also discussed. 相似文献
6.
We investigate the hypothesis that the observed weak interactions are the residual interactions of quasi Goldstone fermions. Left-handed quarks and leptons arise from the spontaneous symmetry breaking U(6) → U(4) × SU(2) in a supersymmetric theory. The simplest preon model realizing this breakdown leads, in the complementary picture, to the supersymmetric extension of the standard model of electroweak interactions. Furthermore, 't Hooft's anomaly conditions are satisfied with respect to the unbroken subgroup of the U(6) flavour symmetry and R-invariance. The preon model predicts the existence of a ninth chiral supermultiplet, the novino. 相似文献
7.
A new model for the substructure of leptons, quarks and weak bosons is investigated. The weak interactions are residual effects due to the substructure. No spontaneous symmetry breaking is needed to generate masses. The structure of the weak interactions at high energies is expected to deviate substantially from the one predicted by the standard SU(2) × U(1) theory. 相似文献
8.
《Physics letters. [Part B]》1986,167(2):209-213
Heavy leptons with high weak isospin, predicted in a subcomponent model of quarks and leptons with SU(2)L × U(1) symmetry, are examined phenomenologically in connection with recently reported anomalous events and super high energy physics. In constructing the effective lagrangian based on the subcomponent structure, IW = 1 heavy leptons play a special role in the effective interaction. 相似文献
9.
We show that the usual three families of quarks and leptons are identifiable with quasi Nambu-Goldstone fermions in a supersymmetric non-linear realization of E7 corresponding to the Kähler manifold E7/SU(5) × SU(3) × U(1). So the triplication of families suggests the underlying preon theory realizing the global E7 linearly. Possible connections with N = 8 supergravity are also discussed. 相似文献
10.
Experiments in progress with hydrogen and deuterium may in practice determine the fundamental parameters and constituents of the weak interaction within the framework of unified gauge theories. In particular, for SU (2) × U (1) theories, from the results of these experiments one can infer the masses of the charged and neutral weak vector bosons (and thus sin2θW), and the isospin classification of the right-handed portions of the electron and the u- and d-quarks. Non-singlet assignments for eR, uR and dR would imply the existence of additional leptons and/or quarks. Hydrogen/deuterium data also may be used to discriminate between SU (2) × U (1) models and various models based on larger gauge groups. 相似文献
11.
We discuss models of weak interactions which can account for the recently observed μ?μ?μ+ events in vμ reactions by allowing for the production of a new heavy neutral lepton and a new quark. One model is based on an SU(3) × U(1) gauge theory in shich the left-handed leptons are classified in anti-triplets. The second model catagorizes the leptons in an octet in accord with the more restrictive SU(3) weak gauge theory. 相似文献
12.
Haim Harari 《Physics Reports》1978,42(4):235-309
We review the physics of quarks and leptons within the framework of gauge theories for the weak and electromagnetic interactions. The Weinberg-Salam SU(2) × U(1) theory is used as a “reference point” but models based on larger gauge groups, especially SU(2)L × SU(2)R × U(1), are discussed. We distinguish among thre “generations” of fundamental fermions: The first generation (e?, νe, u, d), the second generation (μ?, νμ, c, s) and the third generation (τ?, ντ, t, b). For each generation we discuss the classification of all fermions, the charged and neutral weak currents, possible right-handed currents, parity and CP-violation, fermion masses and Cabibbo-like angles and related problems. We review theoretical ideas as well as experimental evidence, emphasizing open theoretical problems and possible experimental tests. The possibility of unifying the weak, electromagnetic and strong interactions in a grand unification scheme is reviewed. The problems and their possible solutions are presented, generation by generation, but a brief subject-index (following the table of contents) enables the interested reader to follow any specific topic throughout the three generations. 相似文献
13.
Four families of composite quarks and leptons, two standard and two non-standard, are found in a unique solution SU(3)HC × SU(6)L × SU(6)R of a restricted 't Hooft anomaly-matching program. Testable predictions emerge, such as prohibition of μ → eγ, zero charge asymmetry in e+e? → τ+τ? in contrast to e+e? → μ+μ?, and a rich new hadron spectrum masses around MW. A minimal set of spectator fermions contains color-singlet objects with fractional quark-like charges. 相似文献
14.
C. R. Das L. V. Laperashvili A. Tureanu 《The European Physical Journal C - Particles and Fields》2010,66(1-2):307-324
We have developed the concept of parallel existence of the ordinary (O-) and mirror (M-), or shadow (Sh-) worlds. In the first part of the paper we consider a mirror world with broken mirror parity and the breaking E 6→SU(3)3 in both worlds. We show that in this case the evolutions of coupling constants in the O- and M-worlds are not identical, having different parameters for similar evolutions. E 6 unification, inspired by superstring theory, restores the broken mirror parity at the scale ~1018 GeV. With the aim to explain the tiny cosmological constant, in the second part we consider the breakings: E 6→SO(10)×U(1) Z in the O-world, and E′6→SU(6)′×SU(2)′ θ in the Sh-world. We assume the existence of shadow θ-particles and the low-energy symmetry group SU(3)′ C ×SU(2)′ L ×SU(2)′ θ ×U(1)′ Y in the shadow world, instead of the Standard Model. The additional non-Abelian SU(2)′ θ group with massless gauge fields, “thetons”, has a macroscopic confinement radius 1/Λ′ θ . The assumption that Λ′ θ ≈2.3?10?3 eV explains the tiny cosmological constant given by recent astrophysical measurements. In this way the present work opens the possibility to specify a grand unification group, such as E 6, from cosmology. 相似文献
15.
A class of supersymmetric preon models is considered in which the hypercolour groupG
HC and the unbroken flavour groupG
f anomalies are zero without needing spectators. It is shown that forG
HC=SU(2) and SU(3) quarks and leptons as composites can be obtained satisfying ’t Hooft’s anomaly matching conditions. For the
case ofG
HC=SU(3),G
f can accommodate a horizontal symmetry group to describe just three generations. 相似文献
16.
E.P. Shabalin 《Nuclear Physics B》1976,103(2):371-380
An SU(3) × U(1) × U(1)′ gauge model of weak and electromagnetic interactions is proposed which satisfies the rule for non-leptonic decays of strange particles. The value of neutral leptonic currents predicted in the model agrees with the experimental data. 相似文献
17.
We describe a class of supersymmetric SU(3)×SU(2)×U(1) models where all quarks and leptons, as well as their scalar partners, get masses through one-loop radiative corrections. 相似文献
18.
We assume weak, electromagnetic and strong interactions to be asymptotically divergent, and to become strong at very large energies, of the order of the Plank mass. In this picture, the “low-energy” couplings (i.e. in the 102 GeV region) must be near the infrared stable point, and this allows us to put bounds on the number of elementary fermions (quarks and leptons). Similar assumptions on the Higgs couplings give bound on the fermion and on the Higgs boson masses. We consider the cases where weak and electromagnetic interactions are described by the gauge groups SU(2) ? U(1) or SU(2)R ? U(1). The weak neutral current mixing angle is computed in both cases. 相似文献
19.
We study the possibility that theU(1) B global symmetry associated with baryon number is spontaneously broken. We present realistic examples implemented in the context of a suitably extended standardSU(2) L×U(1)×SU(3)c model and of a composite model of quarks and leptons. The globalU(1) B symmetry in both cases is spontaneously broken at a relatively low mass scale without any conflict with observations. The dominant baryon number nonconserving process in these models obeys the ΔB=2 selection rule. 相似文献
20.
We present a model based on the gauge group G = GHC × GS × SU(2)L × U(1), where the hypercolour gauge group GHC is responsible for the dynamical breaking of the strong group GS to SU(3)C of QCD. Chiral symmetry breaking of high-colour representations produces dynamical breaking of the electroweak SU(2)L × U(1) gauge group. Fermion masses and flavour mixing are dynamically generated from the condensations of high-colour representations. A phenomenological analysis of the model is also presented. 相似文献